1. Field of the Invention
This invention pertains to signal or data transmission through fiber optic cables. More particularly, this invention pertains to a connector module with monitoring capabilities for use in such a transmission system.
2. Description of the Prior Art
The telecommunications and data transmission industries are rapidly expanding their development of fiber optic transmission systems. Historically, telecommunications signals and data have been transmitted over wire lines such as twisted pair wire or coaxial cables. In order to accommodate higher signal rate speeds, the industry is turning to increased use of fiber optic cables as the transmission medium.
As the use of fiber optic cables increases, the need for peripheral equipment has increased. For example, it is desirable to have access to a fiber optic line for the purpose of either rerouting the line in the event of damage to the line or to have access to the line for purposes of monitoring or testing the line.
Fiber optic peripheral equipment for cable management, cable storage and connection capabilities are well known. The use of modular fiber optic connector modules is known for performing so-called cross connect applications. In FIG. 1 of the present application, an optical cross connect module of the prior art is shown. With reference to that figure, the module 10 includes a housing 12 which contains a 2-by-4 fiber optic switch 14 and a fiber optic beam splitter 16. A transmit fiber optic connector 18 and a receive fiber optic connector 20 are secured to the back panel 22 of the housing 12. On the front panel 24 of the housing, the fiber optic connectors 26, 28, 30, 32 and 34 are secured to provide transmit line monitoring, transmit line access, receive line access, transmit line cross-connect and receive line cross-connection, respectively. The splitter 60 receives a signal beam from the transmit connector 18 along a fiber optic cable 36. The splitter 16 directs ten percent of the beam to the monitor connector 36 along the cable 38. The remaining ninety percent of the beam is directed to a fiber optic cable 40.
By rotation of knob 42, an operator can actuate switch 14 to connect cable 40 to either of cables 44,46. Cable 44 is optically connected to connector 28. Cable 46 is optically connected to connector 32. A cable 48 is connected to connector 20. Actuation of the switch 14 results in cable 48 being connected to either of cables 50 or 60 which are connected, in turn, to connectors 30,34. By reason of this structure, with the switch 14 shown in the position of FIG. 1, the normal signal path is from connectors 18,20 to connectors 32,34, respectively. Upon actuation of the switch 14 by turning of knob 42, connection from connectors 18,20 is shifted to connectors 28,30. Connector 26 in combination with beam splitter 16 permits monitoring of the signal along the transmit cable 40 without interruption of the signal.
Connectors 26, 28, 30 are normally not connected to an external cable. Accordingly, to prevent back reflection, the cable connectors 26, 28 and 30 have, in the prior art, been so-called angled connectors to prevent back reflection.
Modules such as module 10 may be utilized for cross-connecting or interconnecting a variety of fiber optic equipment. Equipment which receives a fiber optic signal typically has a signal power window or range for signals to be received by the equipment. For example, a piece of equipment might require that an incoming fiber optic signal be received at -25 db p 5 dbm. The use of splitters 16 in the module 10 of FIG. 1, can result in a power variation. Accordingly, the power of the signal through the module 10 may be sufficiently modified that it is no longer within the desired power window for downstream equipment.
It is an object of the present invention to provide a fiber optic connector module which permits monitoring of a signal while insuring that the signal leaving the module will be within a desired power range for down-stream equipment.